1. Field
One embodiment of the invention relates to an apparatus and method for image coding distortion reduction.
2. Description of the Related Art
When moving images are transferred or recorded, the moving images are coded in order to increase transfer efficiency and compression efficiency. On the other hand, on a receiving or reproducing side where the coded moving images are received, the moving images are decoded. In this case, distortion reduction processing is performed to reduce a coding distortion.
For example, in an image coding distortion reduction apparatus disclosed in PCT National Publication No. 2007-525902, a coding artifact (ringing distortion reduction processing and block distortion reduction processing) is controlled in accordance with a value (global indicator value) which is obtained by a given computation expression using, for example, quantization information and coding amount information. The ringing distortion reduction processing and the block distortion reduction processing are uniformly controlled by the global indicator value.
Another technique for reducing coding distortion is described in Jpn. Pat. Appln. KOKAI Publication No. 2006-325155. According to this document, image processing using motion compensation is performed in accordance with the appearance of the coding distortion.
According to a conventional method of reducing a distortion resulting from the coding of moving images, even if ringing distortion is generated in a situation where an image is almost static, where a coding amount is reduced by motion compensation and where block distortion is not easily generated, the ringing distortion cannot be sufficiently reduced or unnecessary block distortion reduction processing is performed, so that the image may be deteriorated.
Furthermore, even if the distortion reduction processing is always performed uniformly, the distortion reduction efficiency may vary depending on how moving images are coded.